The present invention relates to the use of a machine ground drive control unit with a dual axis control system (joystick) actuator connected with a cam plate and links for operation by manual levers or foot pedal operating linkages. The cam plate is mounted and positioned such that the drive to a self-propelled machine, such as an excavator can be carried out in several different modes of operation.
In the prior art, skid steer loaders and mini-excavators have used separate hydraulic motors for driving wheels or tracks on each side of the machine. The motors on each side of the machine are controlled by valves that permit the motors to be driven in forward and reverse directions. Individual hand levers, foot levers, and joystick controls have been used for forward and reverse drive and for steering. Generally, the joystick controls are dual axis hydraulic or electric controls operated with short hand operated handles operating an actuator disk to move pilot control valves or electric switches that are mounted directly in the operator""s compartment.
Manual levers or foot control levers are preferred for operating the drive train of self-propelled machines such as excavators or loaders, while the convenience of the pilot valves or electric switches used with dual axis joystick controls is desirable. Pilot valves are responsive and compact. The pilot valve assemblies also are high production items that are reasonably priced.
The present invention provides an actuator assembly permitting use of an existing pilot control valve or electric switch normally used with a dual axis joystick control to be used with hand operated levers or foot operated pedals on a self-propelled machine such as an excavator or a skid steer loader for controlling the final drive motors of the machine.
The present invention relates to a linkage for operating a dual axis control assembly such as a pilot valve assembly or an electrical switch, normally used for joystick control, but modified for operation with individual hand operated levers or pivoted foot operated pedals that load linkage rods in tension and compression. In one aspect, as shown, a standard pilot control valve assembly for hydraulic drives is mounted onto a frame member of a machine, specifically an excavator in the form disclosed, and the hand levers or foot pedals are positioned in an operator""s compartment. The pivoting manual control actuators move links that tilt a cam plate that operates the four valves of the pilot control valve assembly selectively to obtain forward, reverse, and directional or steering movement of the controlled drive motors.
The operating cam plate is connected to the linkage through spherical bearings that are positioned in desired locations so that the four pilot valves, which are operated by external plungers arranged at corners of a square layout, can be individually operated. Each of the drive motors can be controlled to drive individually in forward and reverse. The motors also can be simultaneously driven in forward or reverse or can be driven forward on one side of the implement while the opposite side motor is driven in reverse to quickly steer the machine.
The linkage arrangement provides the advantages of an easily operated, compact pilot control valve assembly, normally used for joystick control. The pilot valve can be mounted outside the operator""s compartment for actuation by pivoting hand levers or foot pedal controls in the operator""s platform of the machine.
Pilot valve assemblies are high volume items, which means that they are relatively low in price. The present invention provides pilot valves for ease of operation, as opposed to operating a main hydraulic control valve that moves a large valve spool directly. Hand and foot operator controls are preferred for drive controls so that a boom, bucket and slew functions of an excavator or boom and buckets of skid steer loader still can be operated with hand controls, as is conventional. The dual axis control also can be used for electrical switch control.